gpg: Add property "fpr" for use by --export-filter.

* g10/export.c (push_export_filters): New.
(pop_export_filters): New.
(export_pubkey_buffer): Add args prefix and prefixlen.  Adjust
callers.
* g10/import.c (impex_filter_getval): Add property "fpr".
* g10/main.h (struct impex_filter_parm_s): Add field hexfpr.
--

The push and pop feature will help us to use the export filter
internally in gpg.  Same for the export_pubkey_buffer change.

GnuPG-bug-id: 4856
Signed-off-by: Werner Koch <wk@gnupg.org>

doc/gpg.texi

@@ -2471,6 +2471,10 @@ The available properties are:
   created.  The second is the same but given as an ISO string,
   e.g. "2016-08-17". (drop-subkey)
 
+  @item fpr
+  The hexified fingerprint of the current subkey or primary key.
+  (drop-subkey)
+
   @item primary
   Boolean indicating whether the user id is the primary one.  (keep-uid)
 

g10/export.c

@@ -73,6 +73,17 @@ static recsel_expr_t export_keep_uid;
 static recsel_expr_t export_drop_subkey;
 
 
+/* An object used for a linked list to implement the
+ * push_export_filter/pop_export_filters functions.  */
+struct export_filter_attic_s
+{
+  struct export_filter_attic_s *next;
+  recsel_expr_t export_keep_uid;
+  recsel_expr_t export_drop_subkey;
+};
+static struct export_filter_attic_s *export_filter_attic;
+
+
 
 /* Local prototypes.  */
 static int do_export (ctrl_t ctrl, strlist_t users, int secret,
@@ -198,6 +209,41 @@ parse_and_set_export_filter (const char *string)
 }
 
 
+/* Push the current export filters onto a stack so that new export
+ * filters can be defined which will be active until the next
+ * pop_export_filters or another push_export_filters.  */
+void
+push_export_filters (void)
+{
+  struct export_filter_attic_s *item;
+
+  item = xcalloc (1, sizeof *item);
+  item->export_keep_uid = export_keep_uid;
+  export_keep_uid = NULL;
+  item->export_drop_subkey = export_drop_subkey;
+  export_drop_subkey = NULL;
+  item->next = export_filter_attic;
+  export_filter_attic = item;
+}
+
+
+/* Revert the last push_export_filters.  */
+void
+pop_export_filters (void)
+{
+  struct export_filter_attic_s *item;
+
+  item = export_filter_attic;
+  if (!item)
+    BUG (); /* No corresponding push.  */
+  export_filter_attic = item->next;
+  cleanup_export_globals ();
+  export_keep_uid = item->export_keep_uid;
+  export_drop_subkey = item->export_drop_subkey;
+}
+
+
+
 /* Create a new export stats object initialized to zero.  On error
    returns NULL and sets ERRNO.  */
 export_stats_t
@@ -292,10 +338,12 @@ export_secsubkeys (ctrl_t ctrl, strlist_t users, unsigned int options,
 
 /*
  * Export a single key into a memory buffer.  STATS is either an
- * export stats object for update or NULL.
+ * export stats object for update or NULL.  If PREFIX is not NULL
+ * PREFIXLEN bytes from PREFIX are prepended to the R_DATA.
  */
 gpg_error_t
 export_pubkey_buffer (ctrl_t ctrl, const char *keyspec, unsigned int options,
+                      const void *prefix, size_t prefixlen,
                       export_stats_t stats,
                       kbnode_t *r_keyblock, void **r_data, size_t *r_datalen)
 {
@@ -313,6 +361,8 @@ export_pubkey_buffer (ctrl_t ctrl, const char *keyspec, unsigned int options,
     return gpg_error_from_syserror ();
 
   iobuf = iobuf_temp ();
+  if (prefix && prefixlen)
+    iobuf_write (iobuf, prefix, prefixlen);
   err = do_export_stream (ctrl, iobuf, helplist, 0, r_keyblock, options,
                           stats, &any);
   if (!err && !any)

g10/gpgv.c

@@ -715,12 +715,15 @@ gpg_dirmngr_get_pka (ctrl_t ctrl, const char *userid,
 
 gpg_error_t
 export_pubkey_buffer (ctrl_t ctrl, const char *keyspec, unsigned int options,
+                      const void *prefix, size_t prefixlen,
                       export_stats_t stats,
                       kbnode_t *r_keyblock, void **r_data, size_t *r_datalen)
 {
   (void)ctrl;
   (void)keyspec;
   (void)options;
+  (void)prefix;
+  (void)prefixlen;
   (void)stats;
 
   *r_keyblock = NULL;

g10/import.c

@@ -1478,6 +1478,11 @@ impex_filter_getval (void *cookie, const char *propname)
                     (pk->pubkey_usage & PUBKEY_USAGE_UNKNOWN)?"?":"");
           result = numbuf;
         }
+      else if (!strcmp (propname, "fpr"))
+        {
+          hexfingerprint (pk, parm->hexfpr, sizeof parm->hexfpr);
+          result = parm->hexfpr;
+        }
       else
         result = NULL;
     }

g10/keyserver.c

@@ -1806,7 +1806,7 @@ keyserver_put (ctrl_t ctrl, strlist_t keyspecs)
 
       err = export_pubkey_buffer (ctrl, kspec->d,
                                   opt.keyserver_options.export_options,
-                                  NULL,
+                                  NULL, 0, NULL,
                                   &keyblock, &data, &datalen);
       if (err)
         log_error (_("skipped \"%s\": %s\n"), kspec->d, gpg_strerror (err));

g10/main.h

@@ -390,6 +390,7 @@ struct impex_filter_parm_s
 {
   ctrl_t ctrl;
   kbnode_t node;
+  char hexfpr[2*MAX_FINGERPRINT_LEN + 1];
 };
 
 const char *impex_filter_getval (void *cookie, const char *propname);
@@ -413,6 +414,8 @@ void export_print_stats (export_stats_t stats);
 
 int parse_export_options(char *str,unsigned int *options,int noisy);
 gpg_error_t parse_and_set_export_filter (const char *string);
+void push_export_filters (void);
+void pop_export_filters (void);
 
 int exact_subkey_match_p (KEYDB_SEARCH_DESC *desc, kbnode_t node);
 
@@ -425,6 +428,7 @@ int export_secsubkeys (ctrl_t ctrl, strlist_t users, unsigned int options,
 
 gpg_error_t export_pubkey_buffer (ctrl_t ctrl, const char *keyspec,
                                   unsigned int options,
+                                  const void *prefix, size_t prefixlen,
                                   export_stats_t stats,
                                   kbnode_t *r_keyblock,
                                   void **r_data, size_t *r_datalen);

g10/test-stubs.c

@@ -471,12 +471,15 @@ gpg_dirmngr_get_pka (ctrl_t ctrl, const char *userid,
 
 gpg_error_t
 export_pubkey_buffer (ctrl_t ctrl, const char *keyspec, unsigned int options,
+                      const void *prefix, size_t prefixlen,
                       export_stats_t stats,
                       kbnode_t *r_keyblock, void **r_data, size_t *r_datalen)
 {
   (void)ctrl;
   (void)keyspec;
   (void)options;
+  (void)prefix;
+  (void)prefixlen;
   (void)stats;
 
   *r_keyblock = NULL;